svn commit: r357004 - in head/sys: kern sys

[Hans Petter Selasky]

On 2020-01-23 02:24, Gleb Smirnoff wrote:
> Author: glebius
> Date: Thu Jan 23 01:24:47 2020
> New Revision: 357004
> URL: https://svnweb.freebsd.org/changeset/base/357004
> 
> Log:
>    Enter the network epoch for interrupt handlers of INTR_TYPE_NET.
>    
>    Provide tunable to limit how many times handlers may be executed
>    without reentering epoch.
>    
>    Differential Revision:	https://reviews.freebsd.org/D23242
> 
> Modified:
>    head/sys/kern/kern_intr.c
>    head/sys/sys/interrupt.h
> 
> Modified: head/sys/kern/kern_intr.c
> ==============================================================================
> --- head/sys/kern/kern_intr.c	Thu Jan 23 01:20:59 2020	(r357003)
> +++ head/sys/kern/kern_intr.c	Thu Jan 23 01:24:47 2020	(r357004)
> @@ -48,6 +48,7 @@ __FBSDID("$FreeBSD$");
>   #include <sys/mutex.h>
>   #include <sys/priv.h>
>   #include <sys/proc.h>
> +#include <sys/epoch.h>
>   #include <sys/random.h>
>   #include <sys/resourcevar.h>
>   #include <sys/sched.h>
> @@ -94,6 +95,9 @@ static int intr_storm_threshold = 0;
>   SYSCTL_INT(_hw, OID_AUTO, intr_storm_threshold, CTLFLAG_RWTUN,
>       &intr_storm_threshold, 0,
>       "Number of consecutive interrupts before storm protection is enabled");
> +static int intr_epoch_batch = 1000;
> +SYSCTL_INT(_hw, OID_AUTO, intr_epoch_batch, CTLFLAG_RWTUN, &intr_epoch_batch,
> +    0, "Maximum interrupt handler executions without re-entering epoch(9)");
>   static TAILQ_HEAD(, intr_event) event_list =
>       TAILQ_HEAD_INITIALIZER(event_list);
>   static struct mtx event_lock;
> @@ -587,6 +591,8 @@ intr_event_add_handler(struct intr_event *ie, const ch
>   		ih->ih_flags |= IH_MPSAFE;
>   	if (flags & INTR_ENTROPY)
>   		ih->ih_flags |= IH_ENTROPY;
> +	if (flags & INTR_TYPE_NET)
> +		ih->ih_flags |= IH_NET;
>   
>   	/* We can only have one exclusive handler in a event. */
>   	mtx_lock(&ie->ie_lock);
> @@ -1196,11 +1202,12 @@ ithread_execute_handlers(struct proc *p, struct intr_e
>   static void
>   ithread_loop(void *arg)
>   {
> +	struct epoch_tracker et;
>   	struct intr_thread *ithd;
>   	struct intr_event *ie;
>   	struct thread *td;
>   	struct proc *p;
> -	int wake;
> +	int wake, epoch_count;
>   
>   	td = curthread;
>   	p = td->td_proc;
> @@ -1235,8 +1242,21 @@ ithread_loop(void *arg)
>   		 * that the load of ih_need in ithread_execute_handlers()
>   		 * is ordered after the load of it_need here.
>   		 */
> -		while (atomic_cmpset_acq_int(&ithd->it_need, 1, 0) != 0)
> +		if (ie->ie_hflags & IH_NET) {
> +			epoch_count = 0;
> +			NET_EPOCH_ENTER(et);
> +		}
> +		while (atomic_cmpset_acq_int(&ithd->it_need, 1, 0) != 0) {
>   			ithread_execute_handlers(p, ie);
> +			if ((ie->ie_hflags & IH_NET) &&
> +			    ++epoch_count >= intr_epoch_batch) {
> +				NET_EPOCH_EXIT(et);
> +				epoch_count = 0;
> +				NET_EPOCH_ENTER(et);
> +			}
> +		}
> +		if (ie->ie_hflags & IH_NET)
> +			NET_EPOCH_EXIT(et);
>   		WITNESS_WARN(WARN_PANIC, NULL, "suspending ithread");
>   		mtx_assert(&Giant, MA_NOTOWNED);
>   

Beware that iflib uses GROUP TASKs to invoke the RX-path for packet 
processing and only register a fast IRQ handler.

--HPS